J2K: Convert Java8 lambdas properly

#KT-7149 Fixed

j2k/src/org/jetbrains/kotlin/j2k/ExpressionConverter.kt

@@ -30,6 +30,7 @@ import org.jetbrains.kotlin.builtins.PrimitiveType
 import org.jetbrains.kotlin.j2k.ast.*
 import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.psi.*
+import org.jetbrains.kotlin.psi.psiUtil.getParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.isExtensionDeclaration
 import org.jetbrains.kotlin.resolve.jvm.JvmPrimitiveType
@@ -537,6 +538,50 @@ class DefaultExpressionConverter : JavaElementVisitor(), ExpressionConverter {
         }
     }
 
+    override fun visitLambdaExpression(expression: PsiLambdaExpression) {
+        val parameters = expression.parameterList
+        val convertedParameters = ParameterList(parameters.parameters.map {
+            val paramName = Identifier(it.name!!).assignNoPrototype()
+            val paramType = if (it.typeElement != null) converter.typeConverter.convertType(it.type) else null
+            LambdaParameter(paramName, paramType).assignPrototype(it)
+        }).assignPrototype(parameters)
+
+        val body = expression.body
+        when (body) {
+            is PsiExpression -> {
+                val convertedBody = codeConverter.convertExpression(body).assignPrototype(body)
+                result = LambdaExpression(convertedParameters, Block(listOf(convertedBody), LBrace().assignNoPrototype(), RBrace().assignNoPrototype()))
+            }
+            is PsiCodeBlock -> {
+                val convertedBlock = codeConverter.withSpecialStatementConverter(object: SpecialStatementConverter {
+                    override fun convertStatement(statement: PsiStatement, codeConverter: CodeConverter): Statement? {
+                        if (statement !is PsiReturnStatement) return null
+
+                        val returnValue = statement.returnValue
+                        val methodReturnType = codeConverter.methodReturnType
+                        val expressionForReturn = if (returnValue != null && methodReturnType != null)
+                            codeConverter.convertExpression(returnValue, methodReturnType)
+                        else
+                            codeConverter.convertExpression(returnValue)
+
+                        if (body.statements.lastOrNull() == statement) {
+                            return expressionForReturn
+                        }
+
+                        val callExpression = expression.getParentOfType<PsiMethodCallExpression>(false)
+                        if (callExpression != null) {
+                            return ReturnStatement(expressionForReturn, Identifier(callExpression.methodExpression.text).assignNoPrototype())
+                        }
+
+                        return ReturnStatement(expressionForReturn)
+                    }
+
+                }).convertBlock(body).assignPrototype(body)
+                result = LambdaExpression(convertedParameters, convertedBlock)
+            }
+        }
+    }
+
     companion object {
         private val needQualifierNameSet = setOf("java.lang.Byte", "java.lang.Double", "java.lang.Float", "java.lang.Long", "java.lang.Short")
     }

j2k/src/org/jetbrains/kotlin/j2k/StatementConverter.kt

@@ -222,7 +222,9 @@ class DefaultStatementConverter : JavaElementVisitor(), StatementConverter {
         var block = converterForBody.convertBlock(tryBlock)
         var expression: Expression = Expression.Empty
         for (variable in resourceVariables.reverse()) {
-            val lambda = LambdaExpression(Identifier.toKotlin(variable.getName()!!), block)
+            val parameter = LambdaParameter(Identifier(variable.name!!).assignNoPrototype(), null).assignNoPrototype()
+            val parameterList = ParameterList(listOf(parameter)).assignNoPrototype()
+            val lambda = LambdaExpression(parameterList, block)
             expression = MethodCallExpression.build(codeConverter.convertExpression(variable.getInitializer()), "use", listOf(), listOf(), false, lambda)
             expression.assignNoPrototype()
             block = Block(listOf(expression), LBrace().assignNoPrototype(), RBrace().assignNoPrototype()).assignNoPrototype()
@@ -252,6 +254,7 @@ class DefaultStatementConverter : JavaElementVisitor(), StatementConverter {
             codeConverter.convertExpression(returnValue, methodReturnType)
         else
             codeConverter.convertExpression(returnValue)
+
         result = ReturnStatement(expression)
     }
 

j2k/src/org/jetbrains/kotlin/j2k/ast/Expressions.kt

@@ -124,7 +124,7 @@ class PolyadicExpression(val expressions: List<Expression>, val token: String) :
     }
 }
 
-class LambdaExpression(val arguments: String?, val block: Block) : Expression() {
+class LambdaExpression(val parameterList: ParameterList?, val block: Block) : Expression() {
     init {
         assignPrototypesFrom(block)
     }
@@ -132,8 +132,8 @@ class LambdaExpression(val arguments: String?, val block: Block) : Expression()
     override fun generateCode(builder: CodeBuilder) {
         builder append block.lBrace append " "
 
-        if (arguments != null) {
+        if (parameterList != null && !parameterList.parameters.isEmpty()) {
-            builder.append(arguments)
+            builder.append(parameterList)
                     .append("->")
                     .append(if (block.statements.size() > 1) "\n" else " ")
                     .append(block.statements, "\n")

j2k/src/org/jetbrains/kotlin/j2k/ast/Parameter.kt

@@ -18,15 +18,15 @@ package org.jetbrains.kotlin.j2k.ast
 
 import org.jetbrains.kotlin.j2k.*
 
-abstract class Parameter(val identifier: Identifier,
+abstract class Parameter(val identifier: Identifier, val type: Type?) : Element()
-                         val type: Type?): Element()
 
 class FunctionParameter(identifier: Identifier,
                         type: Type,
                         val varVal: FunctionParameter.VarValModifier,
                         val annotations: Annotations,
                         val modifiers: Modifiers,
-                        val defaultValue: DeferredElement<Expression>? = null) : Parameter(identifier, type) {
+                        val defaultValue: DeferredElement<Expression>? = null
+): Parameter(identifier, type) {
     public enum class VarValModifier {
         None,
         Val,
@@ -52,3 +52,13 @@ class FunctionParameter(identifier: Identifier,
         }
     }
 }
+
+class LambdaParameter(identifier: Identifier, type: Type?) : Parameter(identifier, type) {
+    override fun generateCode(builder: CodeBuilder) {
+        builder append identifier
+
+        if (type != null) {
+            builder append ":" append type
+        }
+    }
+}

j2k/src/org/jetbrains/kotlin/j2k/ast/Statements.kt

@@ -43,9 +43,13 @@ class LabeledStatement(val name: Identifier, val statement: Element) : Statement
     }
 }
 
-class ReturnStatement(val expression: Expression) : Statement() {
+class ReturnStatement(val expression: Expression, val label: Identifier? = null) : Statement() {
     override fun generateCode(builder: CodeBuilder) {
-        builder append "return " append expression
+        builder append "return"
+        if (label != null) {
+            builder append "@" append label
+        }
+        builder append " " append expression
     }
 }
 

j2k/testData/fileOrElement/function/java8Lambdas.java

@@ -0,0 +1,84 @@
+import kotlin.jvm.functions.Function0;
+import kotlin.jvm.functions.Function1;
+import kotlin.jvm.functions.Function2;
+
+public class Java8Class {
+    public void foo0(Function0<String> r) {
+    }
+
+    public void foo1(Function1<Integer, String> r) {
+    }
+
+    public void foo2(Function2<Integer, Integer, String> r) {
+    }
+
+    public void helper() {
+    }
+
+    public void foo() {
+        foo0(() -> "42");
+        foo0(() -> { return "42"; });
+        foo0(() -> {
+            helper();
+            return "42";
+        });
+
+        foo1((i) -> "42");
+        foo1(i -> { return "42"; });
+        foo1((Integer i) -> {
+            helper();
+            if (i > 1) {
+                return "42";
+            }
+
+            return "43";
+        });
+
+        foo2((i, j) -> "42");
+        foo2((Integer i, Integer j) -> {
+            helper();
+            return "42";
+        });
+
+        Function2<Integer, Integer, String> f = (Integer i, Integer k) -> {
+            helper();
+            if (i > 1) {
+                return "42";
+            }
+
+            return "43";
+        };
+
+        Function2<Integer, Integer, String> f1 = (Integer i1, Integer k1) -> {
+            Function2<Integer, Integer, String> f2 = (Integer i2, Integer k2) -> {
+                helper();
+                if (i2 > 1) {
+                    return "42";
+                }
+
+                return "43";
+            };
+            if (i1 > 1) {
+                return f.invoke(i1, k1);
+            }
+            return f.invoke(i1, k1);
+        };
+
+        Runnable runnable = () -> { };
+
+        foo1((Integer i) -> {
+            if (i > 1) {
+                return "42";
+            }
+
+            foo0(() -> {
+                if (true) {
+                    return "42";
+                }
+                return "43";
+            });
+
+            return "43";
+        });
+    }
+}

j2k/testData/fileOrElement/function/java8Lambdas.kt

@@ -0,0 +1,86 @@
+// ERROR: 'return' is not allowed here
+// ERROR: Type mismatch: inferred type is kotlin.String but kotlin.Unit was expected
+// ERROR: 'return' is not allowed here
+// ERROR: Type mismatch: inferred type is kotlin.String but kotlin.Unit was expected
+// ERROR: 'return' is not allowed here
+// ERROR: Type mismatch: inferred type is kotlin.String but kotlin.Unit was expected
+public class Java8Class {
+    public fun foo0(r: Function0<String>) {
+    }
+
+    public fun foo1(r: Function1<Int, String>) {
+    }
+
+    public fun foo2(r: Function2<Int, Int, String>) {
+    }
+
+    public fun helper() {
+    }
+
+    public fun foo() {
+        foo0({ "42" })
+        foo0({ "42" })
+        foo0({
+            helper()
+            "42"
+        })
+
+        foo1({ i -> "42" })
+        foo1({ i -> "42" })
+        foo1({ i: Int ->
+            helper()
+            if (i > 1) {
+                return@foo1 "42"
+            }
+
+            "43"
+        })
+
+        foo2({ i, j -> "42" })
+        foo2({ i: Int, j: Int ->
+            helper()
+            "42"
+        })
+
+        val f = { i: Int, k: Int ->
+            helper()
+            if (i > 1) {
+                return "42"
+            }
+
+            "43"
+        }
+
+        val f1 = { i1: Int, k1: Int ->
+            val f2 = { i2: Int, k2: Int ->
+                helper()
+                if (i2 > 1) {
+                    return "42"
+                }
+
+                "43"
+            }
+            if (i1 > 1) {
+                return f.invoke(i1, k1)
+            }
+            f.invoke(i1, k1)
+        }
+
+        val runnable = { }
+
+        foo1({ i: Int ->
+            if (i > 1) {
+                return@foo1 "42"
+            }
+
+            foo0({
+                if (true) {
+                    return@foo0 "42"
+                }
+                "43"
+            })
+
+            "43"
+        })
+    }
+}

j2k/tests/org/jetbrains/kotlin/j2k/JavaToKotlinConverterForWebDemoTestGenerated.java

@@ -2242,6 +2242,12 @@ public class JavaToKotlinConverterForWebDemoTestGenerated extends AbstractJavaTo
             doTest(fileName);
         }
 
+        @TestMetadata("java8Lambdas.java")
+        public void testJava8Lambdas() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/function/java8Lambdas.java");
+            doTest(fileName);
+        }
+
         @TestMetadata("lineBreaksBetweenParameters.java")
         public void testLineBreaksBetweenParameters() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/function/lineBreaksBetweenParameters.java");

j2k/tests/org/jetbrains/kotlin/j2k/JavaToKotlinConverterSingleFileTestGenerated.java

@@ -2242,6 +2242,12 @@ public class JavaToKotlinConverterSingleFileTestGenerated extends AbstractJavaTo
             doTest(fileName);
         }
 
+        @TestMetadata("java8Lambdas.java")
+        public void testJava8Lambdas() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/function/java8Lambdas.java");
+            doTest(fileName);
+        }
+
         @TestMetadata("lineBreaksBetweenParameters.java")
         public void testLineBreaksBetweenParameters() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("j2k/testData/fileOrElement/function/lineBreaksBetweenParameters.java");